Role of the mitochondrial calcium uniporter in brown fat physiology

 描述(由申请人提供)：胰岛素抵抗和2型糖尿病(T2D)是一种具有潜在灾难性经济影响的全球健康危机。仅在美国，就有超过1亿人患有肥胖症，这是糖尿病前期和糖尿病综合征的主要风险因素。最近，人们对通过增强棕色脂肪的活性来治疗肥胖、T2D和相关的代谢紊乱有广泛的兴趣，棕色脂肪是一种能够通过解偶联的伯氧化来燃烧多余脂肪储存的组织。然而，目前对棕色脂肪代谢的调节还不完全清楚，也不清楚这种组织如何在全身能量平衡中发挥其有希望的治疗效果。这项建议旨在通过询问线粒体钙单一转运体的作用来促进对基本棕色脂肪生理学的理解，该通道的分子身份最近被申请人的实验室阐明。单转运体将ATP的产生与细胞的能量需求结合在一起，并可能通过其调节TCA循环通量和回旋的能力在燃料转换中发挥关键作用。单转运体与多种组织中的肾上腺素能信号有关，并支持骨骼肌的峰值生物能量学，骨骼肌是棕色脂肪的发育和代谢近亲；此外，棕色脂肪线粒体I的单转运体电流密度是所有组织中最高的之一。因此，单转运蛋白是调节棕色脂肪代谢以响应激素刺激的一个很有前途的候选者。申请者将追求核心假设，即单一转运蛋白在棕色脂肪生理中的两个互补但不相互依赖的特定目的中发挥核心作用。在目标1中，将在永生化的棕色脂肪细胞中去除单转运蛋白的孔形成亚单位(MCU)，并将分析得到的细胞系在生物能量学、新陈代谢、应激信号和钙动力学方面的缺陷。令人兴奋的初步数据表明，缺乏MCU的棕色脂肪细胞表现出钝化的儿茶酚胺刺激的呼吸；这些结果将得到严格的验证和机械解剖。在目标2中，将在小鼠的棕色脂肪中删除MCU，并将对由此产生的动物进行能量消耗和棕色脂肪活动的改变、耐寒、增加对饮食诱导的肥胖的易感性和胰岛素抵抗的检测。申请人的实验室已经产生了携带条件性MCU等位基因的小鼠，这种等位基因可以用来以组织特异性的方式消除单一转运蛋白的活性。通过在棕色脂肪中建立单一转运体的角色，这一WRK将对这种组织的生理学产生基础性的见解，为其临床应用改善T2D和肥胖症奠定基础。这项工作还将补充拟议的培训计划，使申请者能够发展成为一名成熟、严谨的科学家，具有跨各种专题学科进行交流的能力。

 DESCRIPTION (provided by applicant): Insulin resistance and type 2 diabetes (T2D) represent a global health crisis of potentially disastrous economic impact. In the United States alone, over one hundred million individuals suffer from obesity, the leading risk factor for pre-diabetic and diabetic syndromes. Recently, there has been widespread interest in treating obesity, T2D, and associated metabolic disorders by enhancing the activity of brown fat, a tissue capable of burning excess lipid stores via uncoupled ß-oxidation. At present, however, the regulation of brown fat metabolism is incompletely understood, and it is unclear how this tissue exerts its therapeutically promising effects on systemic energy homeostasis. This proposal aims to advance the understanding of fundamental brown fat physiology by interrogating the role of the mitochondrial calcium uniporter, a channel whose molecular identity was recently elucidated by the applicant's laboratory. The uniporter couples ATP production to cellular energy demand, and may play a key role in fuel switching through its ability to regulate TCA cycle flux and anaplerosis. The uniporter is linked to adrenergic signaling in multiple tissues and supports peak bioenergetics in skeletal muscle, a close developmental and metabolic relative of brown fat; in addition, uniporter current density in brown fat mitochondria i among the highest measured in any tissue. The uniporter is therefore a promising candidate to regulate brown fat metabolism in response to hormonal stimuli. The applicant will pursue the core hypothesis that the uniporter plays a central role in brown fat physiology in two complementary but not codependent specific aims. In Aim 1, the uniporter's pore- forming subunit (MCU) will be ablated in immortalized brown adipocytes, and the resulting cell lines will be analyzed for defects in bioenergetics, metabolism, stress signaling, and calcium dynamics. Exciting preliminary data indicate that brown adipocytes lacking MCU exhibit blunted catecholamine-stimulated respiration; these results will be rigorously validated and dissected mechanistically. In Aim 2, MCU will be deleted in brown fat in mice, and the resulting animals will be assayed for altered energy expenditure and brown fat activity, cold intolerance, increased susceptibility to diet-induced obesity, and insulin resistance. The applicant's laboratory has already generated mice harboring a conditional MCU allele that can be used to ablate uniporter activity in a tissue-specific manner. By establishing a role for the uniporter in brown fat, this wrk will yield foundational insights into the physiology of this tissue, laying the groundwork for its clinical exploitation to ameliorate T2D and obesity. The work will also complement the proposed training plan, enabling the applicant to develop into a mature, rigorous scientist with the abilityto communicate across a variety of topical disciplines.